This invention relates to a flexible support for a transfer roller of a reproduction apparatus.
In the art of commercial copiers and printers, in the transfer process, the use of a noncompliant intermediate transfer member to transfer a toner image from an imaging member to a print media (e.g., paper) is well known. Both Rimai et al. (U.S. Pat. No. 5,084,735, issued on Jan. 28, 1992) and Zaretsky et al. (U.S. Pat. No. 5,370,961, issued on Dec. 6, 1994) show that by using an intermediate transfer roller (IT), composed of a thick compliant layer with a relatively thin stiff overcoat, the quality of toner transfer is improved when compared to non-compliant intermediates. Zaretsky (U.S. Pat. No. 5,187,526, issued on Feb. 16, 1993) describes that transfer can be improved by separately specifying the resistivity of the IT and the second transfer roller, which forms a nip for transfer to paper. Bucks et al. (U.S. Pat. No. 5,701,567, issued on Dec. 23, 1997) describes an IT having electrodes embedded in a compliant blanket to spatially control the applied transfer field. Tombs et al. (WO Patent Application No. 98/04961, dated Feb. 5, 1998) describes the use of a compliant IT in conjunction with a transport web in a multicolor electrophotographic machine. May et al. (U.S. Pat. No. 5,828,931, issued on Oct. 27, 1998 and U.S. Pat. No. 5,715,505, issued on Feb. 3, 1998) describe a compliant imaging member including a thick compliant blanket coated with a thin photoconductive material. The above-mentioned patents describe the benefits of using a compliant layer. However, the compliant layer complicates image-to-image registration of different colors on the print media.
In view of the above, the purpose of this invention is to improve image-to-image registration in multicolor electrophotographic or electrostatographic reproduction apparatus when using a compliant layer intermediate transfer roller by providing a flexible mount for the intermediate transfer roller (IT). The IT mount can be used in apparatus that either collect different color images in register on the IT then transfer them to print media (see FIGS. 7 and 9 of aforementioned WO 98/04961), or in apparatus that collect images in register on paper such as in parallel machines (see FIG. 8 of aforementioned WO 98/04961). An additional embodiment of the apparatus according to this invention collects the image on the print media using sequential passes of the media through the IT transfer nip where only a single IT is used.
The IT mount according to this invention includes sheet metal flexures (i.e., leaf springs) that constrain five degrees of freedom of the IT in an advantageous way. The leaf springs passively adjust the engagement between the IT and the photoconductor drum (PC). This adjustment is driven by the runout of PC and the IT. The amount of adjustment is mainly determined by the stiffness of the sheet metal flexures. By changing the dimensions or material properties of the leaf springs, the adjustment can be chosen such that the effect of the PC and IT runout on the color-to-color registration is greatly reduced. In addition, the changes in engagement due to runout in the PC and the IT is reduced significantly.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.